In the latest skirmish in a long-running dispute over the bones of a 9300-year-old American known as Kennewick Man, the Army Corps of Engineers this week is dumping tons of boulders on the site where the bones were found. Under the 1990 Native American Graves Protection and Repatriation Act, the corps wants to turn the skeleton over for reburial to the Umatilla Tribe of northeastern Oregon, who claim him as an ancestor. But eight prominent anthropologists who have sued the corps for permission to study the skeleton say that covering the site will bury important information and possibly additional bones. This clash is part of a larger battle over who controls American prehistory, pitting Native American religious beliefs against scientists9 desire to test their still-evolving theories stemming from recent discoveries indicating an unexpected degree of diversity among the earliest Americans.